Drive device of vibration actuator

Abstract

A drive device of a vibration actuator to cause stable driving of a vibration actuator without causing the occurrence of a cogging phenomenon. In a drive device of a vibration actuator using mechanical vibrating motion of an electromechanical energy converting element which converts electrical energy into mechanical energy, the drive device includes a control circuit to output a control signal of a frequency to drive the electromechanical conversion element, a drive circuit to impress on the electromechanical conversion element an alternating voltage of the same frequency as the drive signal, and a direct current power supply to supply electric power to the drive circuit. The drive circuit has an inductive element connected in series or in parallel with the electromechanical conversion element, and a switching element to open and close at the same frequency as the control signal, connected such that the voltage of the direct current power supply is impressed thereon. The control circuit limits the range of variation of the frequency of the control signal, based on the current value which flows in the switching element.

What is claimed is: 
     
       1. A drive device of a vibration actuator comprising: a control circuit to output a control signal of a frequency which is to drive an electromechanical conversion element;   a drive circuit to impress on te electromechanical conversion element an alternating voltage of the same frequency as the control signal; and   a direct current power supply to supply electric power to the drive circuit,   wherein the drive circuit includes an inductive element connected in series or in parallel with the electromechanical conversion element, and a switching element to open and close at the same frequency as the control signal, connected such that voltage of the direct current power supply is impressed on the inductive element, and   wherein the control circuit limits the range of variation of the frequency of the control signal, based on a value of the current which flows in the switching element.   
     
     
       2. A drive device of a vibration actuator according to claim 1, wherein the control circuit includes a current detection circuit to detect the value of the current flowing in the switching element; a comparison circuit to compare an output value of the current detection circuit with a predetermined value; and   a circuit to limit a lowest value of a frequency of the control signal, based on an output of the comparison circuit.   
     
     
       3. A drive device of a vibration actuator comprising: a drive circuit including an inductive element connected in series or in parallel with an electromechanical conversion element of the vibration actuator, a switching element to open and close at the same frequency as a control signal, and a resistive element connected in series with the inductive element when the switching element is on.   
     
     
       4. A drive device of a vibration actuator according to claim 3, further comprising a power source connected to said inductive element. 
     
     
       5. A drive device of a vibration actuator according to claim 3, further comprising a control circuit to output a control signal of a frequency to drive said electromechanical conversion element of said vibration actuator. 
     
     
       6. A drive device of a vibration actuator according to claim 5, wherein the control circuit limits the range of variation of the frequency of the control signal, based on a value of the current which flows in the switching element. 
     
     
       7. A drive device of a vibration actuator according to claim 5, wherein the control circuit includes a current detection circuit to detect the value of the current flowing in the switching element; a comparison circuit to compare an output value of the current detection circuit with a predetermined value; and   a circuit to limit a lowest value of a frequency of the control signal, based on an output of the comparison circuit.   
     
     
       8. A drive device of a vibration actuator according to claim 3, further comprising an RS flip flop connected to an output of said drive circuit. 
     
     
       9. A drive device of a vibration actuator according to claim 8, further comprising a comparator disposed between said RS flip flop and said drive circuit. 
     
     
       10. A method of driving a vibration actuator using a drive circuit having an inductive element in series or in parallel with an electromechanical conversion element of the vibration actuator, a switching circuit that opens and closes at the same frequency as a control signal from a control circuit, and a resistive element in series with the inductive element when the switching element is on, the method comprising: supplying a drive signal to the vibration actuator from a connection between the inductive element and the switching element; and   controlling a frequency at which the vibration actuator is driven by limiting a range of frequency of the control signal, based on a value of the current flowing in the switching element.